Surface chemistry of 2-butanol and furfural on Cu, Au and Cu/Au single crystals

Abstract

In this study, the adsorption of 2-butanol and furfural was investigated on Au (111), Cu (111) and Cu/Au (111) surfaces. It was hoped that by studying how these species adsorbed on these surfaces , insight would be provided into the roles of Cu and Au in the “hydrogen free” hydrogenation of furfural to furfuryl alcohol. This is a valuable process as currently furfuryl alcohol is derived from crude oil but it is possible to derive furfural from corn husk making it a greener process. The surfaces were studied under ultra-high vacuum conditions using scanning tunnelling microscopy, thermal desorption spectroscopy and high resolution electron energy loss spectroscopy. The mixed metal systems were prepared via metal vapour deposition of Cu onto a Au (111) single crystal. From the data generated it was found that on Cu, 2-butanol adsorbed primarily at the step edges and surface defects at room temperature resulting in the formation of butanone as well as small amounts of propanal and ethane. On gold there is very limited adsorption resulting in species adsorbed with a random orientation with respect to the surface. On the mixed metal system, it was discovered that the order of the butanol and copper dosing has a significant effect on the orientation of the adsorbed species as well as the surface morphology. However the TDS results suggest that the surfaces are chemically similar. When furfural was dosed on the Cu (111) surface it was found to break down into small chain hydrocarbons and CO species. The furfural formed small chain like features on the surface. On the mixed metal system, the furfural appears to adsorb on top of the copper islands causing a loss of resolution in STM measurements.